Jacqui Cheng’s report on the Snow Leopard rumors suggests, in the headline, that it “may be pure Cocoa”, and in the article:

Something else that may happen is that Apple may eventually wrap everything in Cocoa—things that are currently only Carbon accessible will be no longer. This (which is reportedly not yet in stone) should make many Objective-C programmers happy, although those who are married to Carbon may get a bit bristly at the news. (Note: There may be some disagreement here as to what exactly “Cocoa-only” means, so take that into account when thinking about this. For example, Apple may only axe Carbon UI stuff.)

The “pure Cocoa” stuff is about additional Cocoa wrappers for APIs that currently are only available in Carbon (and/or at the BSD level) — more stuff that developers can do using Objective-C APIs. It is not about dropping Carbon from the OS, which would make no sense. It’s a message for developers, not a description of Snow Leopard.